Looper driving device with periodically variable speed in zig-zag chainstitch sewing machines

ABSTRACT

The invention relates to an improved means for driving the looper device of a sewing machine of the type which sews a chainstitch in a zig-zag pattern. According to the invention, the looper is oscillated respectively at different speeds in mutually perpendicular directions.

United States Patent [19 Marforio' p n 3,783,810 Jan. 8, 1974 1 LOOPER DRIVING DEvICE WITH PERIODICALLY VARIABLE SPEED IN ZlG-ZAG CHAINSTITCH SEWING MACHINES [75] Inventor: Nerino Marforio, Milan, Italy [73] Assignee: S.p.A. Virginio Rimoldi & C., Milan,

Italy 22 Filed: Nov. 9, 1911 211 Appl. No.: 196,974

"BUT" fFoi-"eigri Application PPioI-ity Data Nov. 18, 1970 Italy ..3l873A/70 [52] U.S.'Cl. 112/159, 2/200 [51] Int. Cl, D05b 3/02, D05b H06 [58] Field of Search 112/34, 157, 158,

[56] References Cited UNITED STATES PATENTS 3,285,210 'l-l/l966 v'Iretow et al. ll2/l99 3,301,207 l/1967 Reeber et a1. 3,628,481 12/1971 Gross FOREIGN PATENTS OR APPLICATIONS 285,60l 2/1928 Great Britain 112/200 Primary Examiner-Werner H. Schroeder Attorney-Richard K. Stevens et a1.

[5 7] ABSTRACT The invention relates to an improved means for driving the looper device of a sewing machine of the type which sews a chain-stitch in a zig-zag pattern. According to the invention, the looper is oscillated respectively at different speeds in mutually perpendicular directions.

7 Claims, 3 Drawing Figures PATENTED JAN 8 5 4 SHEET 1 [1F 3 LOOPER DRIVING DEVICE WITH PERIODICALLY VARIABLE SPEED IN ZIG-ZAG CHAINSTI'ICII SEWING MACHINES The herewith described invention refers to a looper driving device with periodically variable speed in zigzag chainstitch sewing machines. It is well-known that the looper covers a practically elliptical path for the zig-zag stitch formation. At the same time the needle covers successively two parallel paths vertical and with a distance between them according to the stitch bight. The fabric to be sewn is dragged by the feed dogs in the well known way. The looper path is normally covered at constant speed and is given by the combination of two oscillatory movements with direction practically I The zig-zag stitch bight, meant as distance between the paths covered alternatively by the needle, changes according to the requirements. If the bight is too large, for example 6 mm or larger, there arises difficulties in the stitch formation when the needle covers the path on the left in respect of the centre of theseam if you look from the sideof'the fabric feeding. In fact, along this path the needle reaches the greatest distance from the starting point of the formation cycle of the looper stitches (lowest point, on the right). As the looper is provided with a constant speed, it does not often succeed in getting into the loop formed by the needle thread while it is'cor'ning up. There derives a trouble which is known as stitch skipping, which can occur often and damage the two edges ofthe fabric. With the aim at eliminating this trouble numerous devices have been designed. A first looper driving device is meant for the periodical movement of the starting point of the looper according to whether the needle is on the left or on the right ofthe centre of theseam. In order to obtain this, the pin around which the looper bracket is 'oscillating is moved alternatively and its movements are in accordance with the needle ones.

A second looper driving device is meant-to variate the'oscillation amplitude of the looper bracket at each variation of the amplitude of the'movements made by the needle. The first of the well known devices has the disadvantage of the different positioning'of the looper in comparison with the needle in correspondence with the lowest and highest position of the'latter. Y

, The movement of the bracket pin causes a different inclinationof the loop in relation to the needle according to whether the latter is on one side or the other of the centre of the seamv and this influences negatively the shedding of the needle thread loop during the formation of the stitch on the left.

The second device is disadvantageous because it requires the exact regulation of the adjusting device controlling the looper oscillations at each variationof the amplitude of the oscillations of the needle. The speedv of the looper movement is constant in both devices.

The here described invention aims at eliminating the mentioned troubles thus obtaining the correct stitch formation independently from its bight.

' The problem has been in particular solved by setting the looper when it must form the stitch on the left of the centre of the seam in a speed higher than that it has when forming the stitch on the right of the centre of the seam. The greater distance between the looperand the needle isjthus counterbalanced by-a speed increasez the looper is therefore fitted with a speed sufficient for it to enter the thread loop formed by the needle in any case.

To this purpose the present invention refers to a looper driving device in a zig-zag chainstitch sewing machine includingtwo adjusting devices, the first of which is for setting the looper in an oscillatory motion in a direction to seize and shed the needle thread loop:

I the second of these devices sets the said looper in an oscillatory motion in a direction perpendicular to the previous one to avoid the needle after seizing the loop: it is characterized by the fact that the first device includes a periodical variator of speed fitted with a driving part connected with a driven one whose position relative to the driving element is such as to transform the received rotations angularly constant into rotations angularly variable in order to set the looper in movements at different speeds with which is adjustably connected so that this looper slowly moves towards the needle when it is on the right of the centre of the seam and then it quickly goes back to thestarting point; it quickly moves towards the needle when it is on the left of the centre of the seam and slowly goes back after seizing the thread loop.

The main advantage obtained with this invention is that to assure'the same setting between the needle and the looper both with large or small zig-zag stitches. In fact, during the formation of stitches, with a 6-mmor larger zig-zag bight, the looper meets the needle during the stitch formation on the left (more distant from the starting point) in the same conditions as those determined for the stitch on" the right this occurs thanks to the differentiated movement speed. More exactly, during the stitch formation on the right (nearer the starting point) the looper moves forward slowly because the distance to be covered is small; during the formation of .the other stitch on the left, the looper moves forward more quickly to cover the greater distance in the same time, so as to meet the needle in the established position and conditions and then goesback slowly. All this happens during two turns of the main shaft of the machine. e

- The characteristics of this invention are clearer in the following specification in theform of an unlimited example with reference to the enclosed figures of which FIG. 1 is a perspective view of the device here described FIG. '2 is a side section view of the zig-zag sewing machine fitted with device (FIG. 1) V FIG. 3 is -a scheme outline of the periodical speed variator.

With special reference to FIG. 2 we can notice that themachine to which the device here described is attached includes a base 1, a standard 2, and an overhanging bracket arm 3.

Inside the base 1 there are placed the looper 28 and the spreader 7 driving devices which are driven by the main shaft 4 of the machine. This shaft is connected with the driving electric motor (not represented) by means of a driving belt 9 which winds round a pulley 8 keyed on this mainshaft 4. Inside the standard 2 there is a vertical shaft 5 which is placed and turns in two brackets 6. It has on the lower end a bevel gear 10 which meshes with a correspondent bevel gear 11 keyed on the main shaft 44 and on the upper end a second bevel gear 10a which meshes with a correspondent bevel gear 11a keyed on a shaft '12 with which the needle l3 and the zig-zag bight regulation driving devices are connected. In particular the zig-zag bight regulation 'devices includes a couple of helical gears 14 and 14a;

the gear 14 is keyed on the shaft 12, while the gear 14a is keyed on a shaft (not visible) perpendicular to the shaft 12 one end of which is placed and turns in the machine frame. On the other end of this shaft a cam 15 is keyed: it turns inside a fork 16 whose strap 17 is fixed to a first linkage lever 18. A second lever 19 is fixed, in an adjustable print, to this first lever 18. One end of the lever 19 is hinged on a part 20 practically tubular keyed on the shaft 21.

This shaft 21 slides in guides 22 fixed to the machine frame. A needle bar gate 23 is fixed to the end of the shaft 21: on the needle bar 24 to which the needle 13 is fixed slides on the gate.

The described device allows the needle to oscillate horizontally.

The needle 13 vertical driving device is formed by a crank 25 keyed on the shaft 12 on whose end the connecting rod 26 is hinged. On the other end of the connecting rod 26 a pin 27 is hinged: it is fixed to the needle bar 24. As the two movements occur at the same time the needle covers, as is known, two rectilinear vertical and parallel paths, the distance between them being pre-determined according to the stitch bight we want to obtain.

With special reference to FIG. 1 we can notice that the looper 28 driving device mounted on the bracket 29 is formed by two adjusting devices the first of which sets the looper in an oscillatory motion shown in the fig. with the arrow A (direction perpendicular to that of the fabric to be seamed (not shown) and meant to carry out the needle thread loop seizing and shedding by the looper. The second device sets the looper in an oscillatory motion too but with direction perpendicular to the previous one shown in the fig. under B, and meant to avoid the looper needle after seizing the thread loop.

Both devices are connected with the main shaft 4 of the machine by means of movement transmitting parts. In particular the first device is formed by a speed reducer connected with the main shaft 4 and made up of two helical gears 30 and 31. The gear 30 with a smaller diameter is keyed on the main shaft 4, while the gear 31 with the greater diameter is keyed on the shaft 32 of the reducer an end of which is placed and turns in the machine frame. The shaft 32 has the rotation axis perpendicular to that of the main shaft 4. The ratio of the two gears is 1 to 2,,so that a turn of themain shaft 4 corresponds to half turn of the shaft 32.

This first device is also formed by a speed overdrive which is formed by two helical gears 33 and 34 meshed together and with a 2 to 1 gear ratio. The gear 33 with a greater diameter is keyed on the shaft 35 whose end is placed and turns in the machine frame, while the gear 34 with the smaller diameter is keyed on the shaft 36 parallel to the shaft 35 and with an end placed and turning in the machine frame.

With this gear ratio each turn of the shaft 35 corresponds to two turns of the shaft 36.

If we carry on referring to FIG. I, we can notice that the speed reducer and the overdrive are connected together by a speed periodical variator formed by a slider 37 fixed to an arm 38 keyed on the shaft 32, the said slider 37 running in a guide 39 fixed to an arm 40 keyed on the shaft 35.

It is to notice that the shafts 35 and 32 are not set on the same axis, but facing and parallel at a predetermined distance. The special setting of these axes makes it possible to transform the constant rotary speed of the main shaft 4 into a variable perpendicular speed of the shaft 36. The choice of a suitable distance makes it possible, as is clearer from the work specification, to obtain a pre-determined speed of the looper 28 for each run it performs during the zig-zag stitch formation. On the free end of the shaft 36 a crank 41 is keyed on which a connecting rod 42 is hinged. The other end of the connecting rod is hinged on a linkage. This linkage is in particular formed by the arm 43 fixed to the arm 44 placed and turning in the machine frame. On this arm 44 a forked lever 45 is keyed, inside which the looper 28 bracketing shaft 46 is placed and turns in an area 47 where this shaft 46 has a practically ring-like groove. The second device is formed by a cam driven by the main shaft and fit to drive the looper bracketing shaft by means of a linkage. The cam is formed by a disc 48 keyed eccentrically on the main shaft 4 and placed in the end practically tubular 49 of a lever 50 where it turns. The other end of the lever 50 is hinged I on a lever whose fulcrum is on the shaft 46. The driving and the resistance arms of this lever are made up respectively of the lever 51 and.52 fixed to a tubular part 53 in which the shaft 46 is placed and turns. The free end of the resistance arm is the fork-shaped 54 lever 52; in this fork 54 a block 55 is placed whose cross section is practically alike that of the fork 54 and fixed to the lever 56. The arms respectively 57 and 58 are fixed to both ends of this lever 56. The arms 57 and 58 are both fixed to the shaft 46 by means of screws 59.

In the FIG. 2 there is shown the thread spreader 7 driving device to carry out stitching when the needle is a little on the left of the centre of the seam. It is formed by a cam mounted on the shaft 4 by means of a linkage.(not visible in the fig.). This cam sets the spreader 7 bracketing shaft 60 in a rotary oscillatory motion. The shaft 60 has in a central part a ring-like groove 61 which is placed and turns in a forked lever 62. The forked lever 62 is hinged on the machine frame with the other end.

An adjusting device not shown sets the forked lever 62 in a rotary oscillatory motion around the frame pivoting axis.

The shaft 60 slides in guides 63. According to this specification the working of the sewing machine as well as that of the looper driving device is quite clear. The pulley 8 driven by the electric motor by means of the belt 9 makes the shaft 4 to rotate: it transmits the movement by means of the bevel gears 10 and 10a to the gears 11 and 11a of the main shaft 4 and the shaft 12 respectively. The helical gear 14 which meshes with the correspondent gear 14a makes the cam 15 to rotate, which, by means of the forked lever 16 and the two levers l8 and 19, transforms the rotary movement of the gear 14a into a lateral and rectlinear alternated movement of the needle bar 24. The crank 25 fixed to the shaft 12 transforms the rotary movement of the shaft 12 into a vertical and rectlinear alternated movement of the needle bar 24. The combination of these movements makes the needle bar 24 and the needle I" with it to cover the paths I and II practically parallel (shown with a dotted line in FIG. 2) with a distance between them indicated with H. This distance H corresponds in particular to the zig-zag bight we want to obtain. The main shaft 4 transmits the movement given to,it by the electric motor to the helical gear 31 by means of the helical gear 30. The ratio between these gears is 1 to 2,

so that the rotation speed of the shaft 32 is half of that of the main shaft. The arm 38 turns at this speed making the guide 39 of the arm 40 to rotate. The rotation speed of this arm is however not constant as the central axis of the shaft 35 is not just placed on the central axis of the shaft 32, being parallel to it. We can notice that the rotation speed of the shaft 35 is in this way periodically variable. FIG. 3 shows schematically the parts forming the periodical speed variator: the driving shaft represented by the shaft 32, the driven shaft represented by the shaft 35, the slider 37 fixed to the driving shaft 32, the guide 30 fixed to the driven shaft 35 and meant to. be connected with the slider 37. During the working of the machine, the slider 37 moves at constant angular speed and each complete turn corresponds to two complete passages, the down and up movements of the neddle on the right of the centre of the scam, the down and up movements of the needle on the left of the centre of the seam.

The working cycle starts with the looper 28 a little on the right with theslider 37 in correspondence with the point 0 of the represented circular path. As soon as the slider starts to rotate, it gives to the guide 39 in correspondence with this path an equal movement in the sense of the arrow C, which means for the looper a run towards the needle which is completely on the right. As the driven shaft 35 is not on the same axis as the driving shaft 32, as the slider 37 moves from point 0 to point '37, the anglecovered by the arm 40 has a value smaller than that of the angle S covered in the same time by the arm 38 fixed to the arm 37. The difference in the values corresponds for the looper'to. a speed which can be thought of as low. This low speedis required by the fact that the looper 28, which iscompletely on the right in correspondence with its starting point, has to cover a short stretch to reach the needle which is also completely on the right and then it must give time to the needle to come up and move to the left of the centre of the seam to carry out the seizing of the looper thread. During the movement of the slider from the point 37' to the point 37", the angle V getsa value greater than that of the angle S and in this case the looper moves with a speed higher than the previous one. As during this cycle the looper makes the back run to the right to carry out the shedding of the needle thread loop, the high peed is required to cover the greater distance between the needle and its own starting point. At this point the slider 37 has reached and passed. the point 37 From this point up to the point 37",the value of the angle V'is greater than that of the angle S, as can be seen from FIG. 3 where V is greater than S, and this because the looper 28 after reaching its starting point;must reverse its movement and carry out the run towards the needle a little on the'left which in the meantime is at the end of its run and has begun coming up thus forming a thread loop. Finally, the slider 37, during the movement from the point 37" to the point 0 imposes to the arm 38 the angles S whose values are greater than those of the angles V, so that correspondingly the speed of the looper 28 movement during the second back run to the right is low. This is due to the fact that during this cycle the looper runs back to the right together with'the needle thus reducing the relative distance which separates both at the begin-.

runs back to the starting point. It quickly moves towards the needle when it is a little on the left during the formation of the next stitch and then slowly runs back after seizing the thread loop. As to second adjusting device we can notice that the constant rotation speed of the main shaft 4 is transformed into an oscillatory movement by the cam 48 which sets the lever 50 as well as the lever represented by the driving 51 and resistance arm 52 in this motion. The lever 56, by means of the forked lever 54, is then made to rotate oscillating on a circle arc around the rotation axis of the shaft 46. An alike rotation in the upper half-plane is set to the looper 28 bracket 29. This oscillation has the direction of the arrow B. The combination of the two movements whose directions have been indicated with A and B makes it possible that at each rotation at constant speed of the main shaft 4 the looper 28 covers the usual path practically elliptical. Modifications can be brought to the invention here described wothout losing in legal protection.

I' claim: I

1. A looper driving device in a zig-zag chainstitch sewing machine having a needle moving between first and second positions comprised by first and second adjusting devices,said first adjusting device comprising means for setting the looper in an oscillatory motion at different speeds being dependent upon the position of said needlein a direction to seize and shed the needle thread loop, said second adjusting device comprising means for setting the looper in an oscillatory motion in adirection perpendicular to the oscillatory motion of said first adjusting device.

2. The looper driving device of claim 1 wherein said first adjusting device comprises a constant speed rotatable shaft interconnected to the looper by means for transforming angularly constant rotations into angularly variable rotations so that the looper is set in a oscillatory motion at different speeds in a direction to seize and shed the needle thread loop thereof.

3. The looper driving device of claim 2 wherein said means include means for reducing angular constant rotations, an overdrive means for transforming variable angular rotations into variable linear speed and a speed periodical variator means for transforming angular constant rotations into angular variable rotations which interconnects the means for reducing the angular constant rotations and the overdrive means.

4. The looper driving device of claim 3 wherein the overdrive means comprise a first shaft, ahelical gear mounted on saidfi'rst shaft, a second shaft, a helical gear mounted on said second shaft, said helical gears meshing, a crank fixed to said second shaft, a rod one end of which is pivotally attached to said second shaft, a first arm one end of which is pivotally attached to the other end of said rod, a second arm fixed to the other end of said first arm, a forked lever fixed at one end thereof to said first arm and a third shaft oscillatably attached to the other end of said forked lever carrying the looper.

5. The looper driving device of claim 3 wherein the speed reducing means comprise a first shaft, a first helical gear fixed to said first shaft, a second shaft and a second helical gear of larger diameter than said first helical gear fixed to said second shaft.

6. The looper driving device of claim 3 wherein the speed periodical variator means comprise an arm fixed to a shaft at one end thereof, a slider attached to'the other end of said arm, a guide slidably connected to said slider at one end thereof, and a second shaft to which is fixed the other end of said guide.

7. A looper driving device in a zig-zag chain-stitch sewing machine comprised by first and second adjusting devices, said first adjusting device comprising a first constant speed rotatable shaft, driven by a second drive shaft through helical gears mounted on said shafts, a first arm fixed at one end thereof to said first shaft, a slider attached to the other end of said first arm, a guide slidably connected to said slider at one end thereof, a third shaft to which is fixed the other end of said guide, a first helical gear mounted on said third shaft, a fourth shaft, a second helical gear mounted on said fourth shaft and meshing with said first gear, a crank fixed to said fourth shaft, a rod one end of which is pivotally attached to said crank, a second arm pivotally attached at one end thereof to the other end of said rod, a third arm to which is fixed the other end of said second arm, a forked lever fixed at one end thereof to said third arm, a fifth shaft oscillatably attached to the other end of said forked lever, and the looper bracketed to said fifth shaft so upon rotation of said second shaft the looper moves slowly towards the needle when the looper is to the right of the center of the seam and then quickly runs back to the starting point, quickly moves towards the needle when the looper is on the left of the center of the seam and slowly moves back to the starting point after seizing the thread loop, said second adjusting device comprising a cam fixed to said second shaft, a first lever one end of which is tubularly mounted on said cam, a second lever pivotally mounted on said fifth shaft and pivotally mounted at one end thereof to the other end of said first lever, the other end of said second lever being of forked-shape, a third lever,the forked-shape end of said second lever being slidably connected to said third lever, fourth and fifth arms connected on either side of said second lever to said third lever at each end thereof and fixed to said fifth shaft at the other end thereof so that upon rotation of said second shaft the looper oscillates directionwise normal to the oscillation created by said first oscillating device whereby a variablespeed elliptical path is followed by the looper when both devices are operating. 

1. A looper driving device in a zig-zag chainstitch sewing machine having a needle moving between first and second positions comprised by first and second adjusting devices,said first adjusting device comprising means for setting the looper in an oscillatory motion at different speeds being dependent upon the position of said needle in a direction to seize and shed the needle thread loop, said second adjusting device comPrising means for setting the looper in an oscillatory motion in a direction perpendicular to the oscillatory motion of said first adjusting device.
 2. The looper driving device of claim 1 wherein said first adjusting device comprises a constant speed rotatable shaft interconnected to the looper by means for transforming angularly constant rotations into angularly variable rotations so that the looper is set in a oscillatory motion at different speeds in a direction to seize and shed the needle thread loop thereof.
 3. The looper driving device of claim 2 wherein said means include means for reducing angular constant rotations, an overdrive means for transforming variable angular rotations into variable linear speed and a speed periodical variator means for transforming angular constant rotations into angular variable rotations which interconnects the means for reducing the angular constant rotations and the overdrive means.
 4. The looper driving device of claim 3 wherein the overdrive means comprise a first shaft, ahelical gear mounted on said first shaft, a second shaft, a helical gear mounted on said second shaft, said helical gears meshing, a crank fixed to said second shaft, a rod one end of which is pivotally attached to said second shaft, a first arm one end of which is pivotally attached to the other end of said rod, a second arm fixed to the other end of said first arm, a forked lever fixed at one end thereof to said first arm and a third shaft oscillatably attached to the other end of said forked lever carrying the looper.
 5. The looper driving device of claim 3 wherein the speed reducing means comprise a first shaft, a first helical gear fixed to said first shaft, a second shaft and a second helical gear of larger diameter than said first helical gear fixed to said second shaft.
 6. The looper driving device of claim 3 wherein the speed periodical variator means comprise an arm fixed to a shaft at one end thereof, a slider attached to the other end of said arm, a guide slidably connected to said slider at one end thereof, and a second shaft to which is fixed the other end of said guide.
 7. A looper driving device in a zig-zag chain-stitch sewing machine comprised by first and second adjusting devices, said first adjusting device comprising a first constant speed rotatable shaft, driven by a second drive shaft through helical gears mounted on said shafts, a first arm fixed at one end thereof to said first shaft, a slider attached to the other end of said first arm, a guide slidably connected to said slider at one end thereof, a third shaft to which is fixed the other end of said guide, a first helical gear mounted on said third shaft, a fourth shaft, a second helical gear mounted on said fourth shaft and meshing with said first gear, a crank fixed to said fourth shaft, a rod one end of which is pivotally attached to said crank, a second arm pivotally attached at one end thereof to the other end of said rod, a third arm to which is fixed the other end of said second arm, a forked lever fixed at one end thereof to said third arm, a fifth shaft oscillatably attached to the other end of said forked lever, and the looper bracketed to said fifth shaft so upon rotation of said second shaft the looper moves slowly towards the needle when the looper is to the right of the center of the seam and then quickly runs back to the starting point, quickly moves towards the needle when the looper is on the left of the center of the seam and slowly moves back to the starting point after seizing the thread loop, said second adjusting device comprising a cam fixed to said second shaft, a first lever one end of which is tubularly mounted on said cam, a second lever pivotally mounted on said fifth shaft and pivotally mounted at one end thereof to the other end of said first lever, the other end of said second lever being of forked-shape, a third lever,the forked-shape end of said second lever being slidably connected to said third lever, fourth and fifth arms conneCted on either side of said second lever to said third lever at each end thereof and fixed to said fifth shaft at the other end thereof so that upon rotation of said second shaft the looper oscillates directionwise normal to the oscillation created by said first oscillating device whereby a variable speed elliptical path is followed by the looper when both devices are operating. 